Method and apparatus for monitoring, dosing and distribution of chemical solutions

ABSTRACT

It is an object of the present invention to provide a system and method for monitoring, dosing and distribution of a chemical composition in a material treatment process, the chemical composition containing at least one additive for maintaining quality of the chemical treatment process. The system and method include: at least one chemical containing unit configured to contain the chemical composition for the chemical treatment process; a dosing unit fluidly communicating with the at least one chemical containing unit configured to receive the chemical composition therefrom and to add a selected dose of the at least one additive to the chemical composition therein; an online monitor configured to monitor a property of the chemical composition at the dosing unit and to transmit a signal corresponding to the monitored property; and a controller programmed and configured to receive the signal from the online monitor and send a signal to the dosing system to add the selected dose to the chemical composition therein in response to the monitored property.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority under 35 U.S.C.§119(e) of U.S. provisional application Ser. No. 60/465,184 filed onApr. 23, 2003, 60/542,741, filed on Feb. 5, 2004, 60/476,931 filed onJun. 9, 2003, and 60/556,864 filed on Mar. 26, 2004, the entire contentsof which are incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO SEQUENTIAL LISTING

Not applicable.

BACKGROUND OF THE INVENTION

1) Field of the Invention

This invention is directed to the field of management of chemicalcompositions used in material treatment processes. This invention isparticularly directed to the field of management of electroplating bathsolutions.

2) Description of the Related Art

Many material treatment processes utilize a chemical composition. Inorder to smoothly operate such a process, upsets or deviations in thequality of the chemical composition should be avoided. Otherwise,quality of the treated material will vary over time. Also, the processmight need to be shut down in order to bring the quality of the chemicalcomposition back into the specification of the process. Such a shutdownis often prohibitively expensive.

Some examples of material treatment processes include chemicalmechanical polishing/planarization (CMP), electrochemicalpolishing/planarization (ECP), or copper electroplating (ECD) ofsemiconductor wafers or coated semiconductor wafers.

Regarding ECD, achieving defect-free copper interconnects on integratedcircuits by electroplating has involved the development of a new processcalled “superfilling” or “bottom-up plating”. Key parts in this processare the organic additives used in the plating bath. These criticalcomponents, called brighteners, suppressors, and levelers, havespecifically been tailored to promote the critical bottom-up plating orsuperconformal deposition that allows high-aspect ratio trenches andvias to be filled correctly. Furthermore, since these additives becomedepleted during the deposition process, bath monitoring, dosing andsolution delivery are critical to process stability, uniform depositionrate, and obtaining the correct physical properties of the copper layer(such as morphology, microstructure, conductivity and grain size).

Presently, copper bath monitoring is performed by measuring thecomposition of the inorganic and organic components in the bath solutioncontained in the reservoir tank of the process tool. This is donecommercially by offline or online methods:

Methods of offline measurements used to analyze bath compositioninclude: titration, high performance liquid chromatography (HPLC),cyclic voltammetric stripping (CVS), and modified CVS. Titration is usedto measure the inorganic components such as copper, acidity andchloride. CVS and HPLC are used to measure the concentration of theorganic additives, the brightener, suppressor and leveler. With respectto CVS, ECI Technology has commercial equipment based on this technique[Bratin P., Chalyt G., Pavlov M., “Control of Damascene Copper Processesby Cyclic Voltammetric Stripping, Plating & Surface Finishing, March2000, pp. 14-16]. With respect to HPLC, Dionex discloses this technique[Dionex Industry Brief; “Analysis of Copper Plating Baths”, pp. 1-8].U.S. Pat. Nos. 6,365,033 and 6,551,479 disclose pulsed voltammetricstripping.

One of the main limitations of CVS is its sensitivity to matrix effectsof the electrolyte, since the copper stripping is dependent not only onthe individual additives but also their interaction and degradation inthe bath solution [Sun, Zhi-Wen and Dixit, Girsih, “Optimized bathcontrol for void-free copper deposition”, Solid State Technology,November, 2001, pp. 97-102; and Taylor, T., Ritzdorf, T., Lindberg F.,Carpenter B., LeFebvre M., “Electroplating bath controls for copperinterconnects”, Solid State Technology, November, 1998]. Also,measurement time tends to be long (several hours) and large volumes ofelectrolytes are used, increasing the consumption and waste stream ofthese expensive chemicals. High performance liquid chromatography (HPLC)also generates large amounts of waste and also has a relatively longresponse time.

Methods of online measurements include periodic sampling of the bath andanalysis at or near the plating tool to monitor bath componentconcentrations. One limitation to many of these methods is that platingbath breakdown products are not measured, although they are critical todetermining bath quality. Some examples of online monitoring include thefollowing. Bratin P., Chalyt G., Pavlov M., “Control of Damascene CopperProcesses by Cyclic Voltammetric Stripping, Plating & Surface Finishing,March 2000, pp. 14-16 disclose several types of online monitor methodsthat measure component concentration by titration and cyclicvoltammetric stripping. A company named Technic, Inc. provides onlineAC/DC voltammetric monitoring. Also, a company named ATMI offerstitration/pulsed cyclic galvanostatic analysis. As another example, U.S.Pat. No. 6,635,157 discloses online titration and CVS. As furtherexamples, U.S. Pat. Nos. 6,365,157 and 6,551,749 disclose online CVSmonitoring.

One of the key objectives electroplating bath management is to maintainconcentrations in the baths at desired levels by consistently dosingadditives and fresh solution (inorganic solution) to counterbalancedepletion of the additives in the bath due to byproduct formation duringplating, degradation, and/or solution bleeding.

Current state-of-the-art dosing and bleeding of the bath is performed atthe reservoir tank of the process tool. For instance, the makeupelectrolyte (inorganic components) is delivered from a sub-fab chemicaldelivery system to the process tool and dosed into the reservoir tank.The additives are stored in small containers in the process tool and aredosed directly into the reservoir tank. Bleeding of the bath is alsoperformed at the reservoir tank. Dosing control is performed by twomethods: open-loop and closed-loop controls.

With regard to open-loop control, U.S. Pat. No. 6,471,845 B1 disclosesempirical equations used for dosage based on previously definedconsumption rates of the various components, and which accounts for thenumber of wafers processed, the plating current density, and otherfactors. As another example, U.S. Pat. No. 6,458,262 B1 discloses achemical consumption process model based on off-line or onlinemeasurements to achieve bath control. As an example, U.S. Pat. No.5,352,350 discloses empirical equations used for online, open loopcontrol of the bath concentrations. These models are tool, chemistry andproduction regime specific. By design, they can, at best, only controlconditioned plating solution around well-known operating conditions.

Others recognize that open-loop control fails to correct for localvariations in consumption associated with plating fluctuations orchanging bath equilibrium as degradation products are formed [Bratin P.,Chalyt G., Pavlov M., “Control of Damascene Copper Processes by CyclicVoltammetric Stripping, Plating & Surface Finishing, March 2000, pp.14-16]. Also, these types of models are likely only valid in thevicinity of a known operating regime and have limited ability toaccommodate process upsets or disturbances. Since open loop control doesnot detect process changes as it assumes steady-state operation, itcould eventually lead to serious copper interconnects defects.

With regard to closed-loop control, bath sampling with either offline oronline analysis is performed as described above. The results are sentback to the process engineer who doses the plating bath accordingly tomaintain it in optimal condition. Offline or online analysis is used to“correct” for concentrations that drift due to incorrect open-loopcontrol. However, current online bath component analysis is performed in20-40 minutes depending on the type of equipment, which is not quite“real-time”. In addition, communication of the online monitor to thedosing system of commercial plating tools is not yet automatic andrequires development of communication protocols to effectively use theprocess signal to control the bath concentrations. U.S. Pat. No.6,592,736 provides one example of a closed-loop control.

As mentioned above, most commercial copper interconnect plating toolsare stand-alone systems where the additives and makeup electrolyte areadded individually to a reservoir tank located inside the plating tooland recirculated to and from the wafer plating cells. A portion of thebath solution in the reservoir tank can be bled out periodically toreduce contamination buildup. However, depending on wafer platingproduction levels, additive bottles may need to be changed quitefrequently at the tool, which increases the risk of operator error andcontamination (for example, from an incorrect bottle exchange).

Online monitoring for concentration control may be integrated into thetool or not. For those tools that do not integrate online monitoringwith the tool, they are disadvantageous because they require processengineer intervention to correct the bath concentrations. Furthermore,most semiconductor fabs or foundries utilize more than one wafer-platingtool in production. Since each tool is controlled separately,inconsistencies in the bath solution between tools can develop which canultimately result in different properties of the copper interconnectdeposit for different tools.

In light of the problems associated with electroplating bath solutionshaving undesirable qualities, a need exists for improvement in themanagement of electroplating bath solutions.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system formonitoring, dosing and distribution of a chemical composition in amaterial treatment process, the chemical composition containing at leastone additive for maintaining quality of the chemical treatment process.The system comprises: at least one chemical containing unit configuredto contain the chemical composition for the chemical treatment process;a dosing unit fluidly communicating with at least one chemicalcontaining unit configured to receive the chemical composition therefromand to add a selected dose of at least one additive to the chemicalcomposition therein; an online monitor configured to monitor a propertyof the chemical composition at the dosing unit and to transmit a signalcorresponding to the monitored property; and a controller programmed andconfigured to receive the signal from the online monitor and send asignal to the dosing system to add the selected dose to the chemicalcomposition therein in response to the monitored property.

It is another object to provide a method for monitoring, dosing anddistribution of a chemical composition in a chemical treatment process,the chemical composition containing at least one additive formaintaining quality of the chemical treatment process. The methodcomprises the following steps. A flow of the chemical composition isallowed from at least one chemical containing unit to a dosing unit. Aproperty of the chemical composition is monitored with an online monitorat a location intermediate to the chemical containing unit and thedosing unit or at the dosing unit. A signal associated with themonitored property is sent by the online monitor to a controller. Thecontroller determines whether at least one additive should be added tothe chemical composition at the dosing unit based upon the monitoredproperty, thereby resulting in a decision to add or not a selectedamount of at least one additive to the chemical composition at thedosing unit based upon the signal from the online monitor. A signalassociated with the decision is sent from the controller to the dosingunit. The selected amount of at least one additive is allowed to beadded or not be added to the chemical composition at the dosing unit inresponse to the signal associated with the decision. The chemicalcomposition is allowed to flow from the dosing unit to the chemicalcontaining unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the inventive system including an optionalchemical dispensing unit.

FIG. 2 is a schematic of an embodiment of the invention also including adosing unit reservoir; a dosage element; a fresh chemical compositionsupply tank; a fluid bleed tank; a conduit allowing the chemicalcomposition to bypass the chemical containing unit; and a conduit/valvearrangement allowing the chemical composition to bypass the dosing unitreservoir, dosage element, fresh chemical composition supply tank, bleedtank, and optional chemical dispensing unit.

FIG. 3 is a schematic of another embodiment of the invention alsoincluding multiple chemical containing units; a dosing unit reservoir; adosage element; a fresh chemical composition supply tank; a bleed tank;a conduit allowing the chemical composition to bypass the chemicalcontaining units; a conduit/valve arrangement allowing the chemicalcomposition to bypass the dosing unit reservoir, dosage element, freshchemical composition supply tank, bleed tank, and optional chemicaldispensing unit; a manifold and reservoir downstream of the chemicalcontaining units; and a second online monitor.

FIG. 4 is a schematic another embodiment of the invention also includingmultiple chemical containing units; a dosing unit reservoir; a dosageelement; a fresh chemical composition supply tank; a bleed tank; aconduit allowing the chemical composition to bypass the chemicalcontaining units; and a conduit/valve arrangement allowing the chemicalcomposition to bypass the dosing unit reservoir, dosage element, freshchemical composition supply tank, bleed tank, and optional chemicaldispensing unit.

FIG. 5 is a schematic of a preferred configuration of the dosageelement.

FIG. 6 is a schematic of a preferred configuration of the optionalchemical dispensing unit.

DESCRIPTION OF PREFERRED EMBODIMENTS

The inventive system allows a chemical composition associated with amaterial treatment process to be monitored, dosed, and distributed to achemical containing unit in which the dosing occurs at a location otherthan at the chemical containing unit. This lessens the risk of operatorerror and contamination because the frequency of changing the additivebottles at the chemical containing unit is decreased. For example, anincorrect bottle exchange will result in contamination.

When there is a plurality of chemical containing units, the risk ofoperator error and contamination is multiplied. Many chemical treatmentfacilities, such as semiconductor fabs or foundries utilize more thanone wafer-plating tool in production. Since each tool is controlledseparately, inconsistencies in the bath solution between tools candevelop which can ultimately result in different properties of thecopper interconnect deposit for different tools. Thus, the invention isespecially advantageous with use with several chemical containing units.

Also, when a controller is integrated with online monitoring, the riskof operator error is lessened because of the relative lack oftransliteration errors made by an operator in between analysis ofoffline data and decisions to add the additives. Thus, in the invention,process engineer intervention is not needed to correct the bathconcentrations.

The controller is analyzer-independent and will not need anymodifications if the bath management system were to be used inconjunction with different instrumentation systems. It only involvessequential discrete control thereby facilitating the control scheme andreducing the implementation cost.

In many prior art system, chemical consumption process model based onoffline or online measurements is utilized to achieve bath control.However, the equation in these types of models are presumably only validin the vicinity of a known operating regime and have limited ability toaccommodate process upsets or disturbances. In contrast, the inventivecontroller does not rely upon a model, but instead makes additivedecisions based upon real time analysis data.

This invention is especially advantageous when implemented in managementof electroplating bath solutions wafer-plating tools in semiconductorfabs or foundries.

With reference to the Figures and Tables I-III, the inventive system andmethod and preferred embodiments thereof are illustrated. TABLE I Firstlegend to reference characters in the figures  10 inventive system  5chemical containing unit  11 optional chemical delivery unit  20 pipingfrom dosing unit to chemical delivery unit  25 conduit  40 conduit  41communication link from controller to online monitor  42 communicationlink from controller to dosing unit  45 dosing unit  55 online monitor 65 controller 100 preferred embodiment of the inventive system 110chemical delivery unit 112 chemical delivery element 120a pressure-feedvessel 1 120b pressure-feed vessel 2 130 blanket gas system 140 conduit150 bypass 151 valve 152 valve 160 day tank 200 controller 210communication link from controller to blending tank unit 220communication link from controller to dosing unit 230 communication linkfrom controller to optional chemical delivery unit 240 communicationlink from controller to monitor 1 245 communication link from controllerto monitor 2 250 communication link from controller to chemicalcontaining unit 250a communication link from controller to chemicalcontaining unit 250b communication link from controller to chemicalcontaining unit 250c communication link from controller to chemicalcontaining unit 250d communication link from controller to chemicalcontaining unit 251 communication link from controller to valve 252communication link from controller to valve 260 communication link fromcontroller solvent supply tank 270 communication link from controller tobleed tank

TABLE II Second legend to reference characters in the figures 300chemical containing element 300a chemical containing element 1 300bchemical containing element 2 300c chemical containing element 3 300dchemical containing element 4 320 inlet to chemical containing element320a inlet to chemical containing element 1 320b inlet to chemicalcontaining element 2 320c inlet to chemical containing element 3 320dinlet to chemical containing element 4 330 outlet from chemicalcontaining element 330a outlet from chemical containing element 1 330boutlet from chemical containing element 2 330c outlet from chemicalcontaining element 3 330d outlet from chemical containing element 4 340chemical containing element outlet manifold 350 chemical containingelement outlet reservoir 360 pump 400 dosing unit reservoir 415 dosingunit circulation pump 420 piping from dosing unit to optional chemicaldelivery unit 425 piping from reservoir to dosage element 426 conduit427a conduit 427b conduit 427c conduit 427d conduit 427e conduit 428athree way valve 428b three way valve 428c three way valve 428d three wayvalve 429a conduit 429b conduit 429c conduit 429d conduit 430 pipingfrom dosage element to reservoir 431 conduit 435 piping from conduit tofluid bleed tank 437 valve 440 pump

TABLE III Third legend to reference characters in the figures 450 dosageelement 460 piping from optional chemical delivery unit to chemicalcontaining unit 461 piping for parallel loop 471 valve 472 dosing pump473 valve 474 flowmeter 480a chemical additive container 480b chemicaladditive container 480c chemical additive container 480d chemicaladditive container 600 fluid bleed tank 610 fluid bleed tank outlet 700fresh chemical composition supply tank 701 piping from fresh chemicalcomposition supply tank to dosing unit 800 monitor 810 piping fromdosing unit 400 to monitor 800 820 piping from monitor 850 monitor 860piping to monitor 870 piping from monitor

As illustrated in FIG. 1, the inventive system includes a chemicalcontaining unit 5 through which the chemical composition flows. Thechemical composition contains certain chemical constituents, such asadditives of the chemical composition which are consumed and/or degradedin a material treatment process. The chemical containing unit 5 isoperatively associated with the material treatment process which occurseither adjacently to chemical containing unit 5 or remotely therefrom.For example, when the chemical containing unit 5 may be located remotelyfrom the material treatment process, it can be part of a larger chemicaldistribution system that incorporates bulk chemical distributionequipment. Preferably, the chemical containing unit is an electroplatingbath reservoir associated with one or more electroplating (ECD) tools inthe clean room of a fab and the dosing unit is located in a chemicalroom located in the sub-fab. More preferably, the electroplating toolsare used to electroplate semiconductor wafers with copper. Alsopreferably, the chemical containing unit is an electrolyte reservoir forsupplying an electrochemical planarization (ECP) electrode system in theclean room of a fab and the dosing unit is located in a chemical roomlocated in the sub-fab. Also preferably, the chemical containing unit isa chemical reservoir for supplying a chemical mechanical planarization(CMP) system in the clean room of a fab and the dosing unit is locatedin a chemical room located in the sub-fab.

The chemical composition flows via conduit 40 to dosing unit 45. Atdosing unit 45, the online monitor 55 monitors a property of thechemical composition. Preferably, the monitored property is aconcentration of one or more chemical constituents of the chemicalcomposition. More preferably, it is the concentration of one or moreadditives or of degradation products resultant from a chemical treatmentprocess associated with the chemical composition operatively associatedwith the chemical containing unit 5.

The online monitor 55 may be any online monitor known to those ordinaryskilled in the art suitable for use in the invention. A preferred onlinemonitor is a “real-time analyzer”, RTA, available from Technic, Inc,Cranston, in R.I., U.S.A.

Another monitor suitable for use in the invention is the ECI systemavailable from ATMI, Danbury, Conn., U.S.A.

The online monitor 55 sends a signal associated with the monitoredproperty to the controller 65 via communication link 41. Based upon thissignal, the controller 65 determines whether or not to add one or moreadditives to the chemical composition at the dosing unit 45, therebyresulting in a decision. The controller 65 sends a signal associatedwith the decision to dosing unit 45 via communication link 42. Basedupon this signal, one or more additives are added or not to the chemicalcomposition at the dosing unit 45. Preferably, the dosing unit 45includes a mixing element so that the chemical composition and anyadditives are well mixed. Preferred examples of additives includebrighteners, suppressors, and levelers.

The chemical composition flows from the dosing unit 45 via conduit 20 tothe optional chemical delivery unit 11. Optional chemical delivery unit11 delivers the chemical composition to the chemical containing unit 5via optional conduit 25. As the chemical delivery unit 11 and conduit 25are optional, the inventive system 10 may be configured such that thechemical composition flows directly from the dosing unit 45 to thechemical containing unit via conduit 20.

As best shown in FIG. 2, a preferred embodiment 100 of the inventivesystem includes a chemical containing unit 300 through which thechemical composition may flow either batch-wise or continuously. Thechemical composition contains certain chemical constituents, such asadditives of the chemical composition which are consumed and/or degradedin a material treatment process. The chemical containing unit 300 isoperatively associated with the material treatment process which occurseither adjacently to chemical containing unit 300 or remotely therefrom.For example, when the chemical containing unit 300 may be locatedremotely from the material treatment process, it can be part of a largerchemical distribution system that incorporates bulk chemicaldistribution equipment.

Preferably, the chemical containing unit 300 includes inlet and outletvalves and a level sensor. When the level sensor senses a selected highlevel, the inlet and outlet valves close thereby preventing the flow ofthe chemical composition thereinto. When desired, an optional conduit461 may be provided through which the chemical composition bypasses thechemical containing unit 300. Thus, the chemical composition maycontinue to flow through the system 100 when the inlet and outlet valvesof chemical containing unit 300 are closed. This bypass flow may beimplemented via signals sent between chemical containing unit 300 andcontroller 200 via communication link 250. This helps continue mixing ofthe chemical composition as well as maintaining a steady flow of itthrough the system, especially if the tool is disconnected.

The chemical composition flows from the chemical containing unit 300 viaconduit 330 to conduit 140, and thenceforth past valve 151 and bypassconduit 150 to dosing unit reservoir 400. Dosing unit reservoir 400 anddosage element 450 together comprise a dosing unit analogous to dosingunit 45. At least a portion of the chemical composition is routed viapiping 810 from the dosing unit reservoir 400 to online monitor 800, atwhich a property of the chemical composition is monitored. Preferably,the monitored property is a concentration of one or more chemicalconstituents of the chemical composition. More preferably, it is theconcentration of one or more additives or of degradation productsresultant from a material treatment process associated with the chemicalcomposition operatively associated with the chemical containing unit300.

The online monitor 800 sends a signal associated with the monitoredproperty to controller 200. Based upon the signal, the controller 200determines whether or not to add one or more additives at dosing unitreservoir 400 to the chemical composition, thereby resulting in adecision. A signal associated with this decision is sent from controller800 via communication link 220 to the dosage element 450. In response tothis signal, the dosage element 450 will or will not add one or moreadditives to the flow of chemical composition through piping 425 todosage element 450. When additives are added to the chemicalcomposition, the chemical composition with the added additives flowsback to dosing unit reservoir 400 via piping 430. Preferably, the dosingunit 450 includes a mixing element so that the chemical composition andany additives are well mixed.

Also based upon the signal from online monitor 800, the controller 200determines whether or not to supply fresh chemical composition viapiping 701 from fresh chemical composition supply tank 700 to dosingunit reservoir 400. Based upon a signal from controller 200 viacommunication link 260, an outlet valve of the fresh chemicalcomposition supply tank 700 opens and a suitable delivery means allowsthe fresh chemical composition to flow therefrom to dosing unit 400.

The fresh chemical composition is understood to be those portions of thechemical composition, excluding any additives added to the chemicalcomposition by dosing unit reservoir 400 and any degradation productsformed as a result of the material treatment process. When the inventionis preferably applied to management of electroplating baths for waferplating tools at a semiconductor fab or foundry, the fresh chemicalcomposition is also referred to as fresh inorganic solution. In thisinstance, the fresh inorganic solution primarily contains CuSO₄, H₂SO₄,and a source of Cl⁻.

Also based upon the signal from online monitor 800, the controller 200determines whether or not to bleed chemical composition at fluid bleedtank 600 via outlet 610. Based upon a signal from controller 200 viacommunication link 270, chemical composition is bled from conduit 420via a valve associated with piping 435. Preferably, the fluid bleed tank600 includes a level sensor. When the level sensor senses a selectedhigh level, an outlet valve of the fluid bleed tank 600 opens andchemical solution exits therefrom via outlet 610. In such a scenario,the valve and level sensor may optionally be associated with controller200 and decisions to allow the chemical composition to exit from outlet610 are made by the controller 200.

The fresh chemical composition at fresh chemical composition tank 700may alternatively include one or more of the additives added to thechemical composition at dosing unit 400 or degradation products from thematerial treatment process. In that case, it contains only minimalconcentrations of them. For example, spent chemical composition bledfrom fluid bleed tank 600 may be regenerated and then stored in freshchemical composition supply tank 700.

With the aid of pump 440, the chemical composition flows from dosingunit reservoir 400 via conduit 420 to optional chemical delivery unit110. Chemical delivery unit 110 includes a means suitable to deliver thechemical composition therefrom to chemical containing unit via optionalconduit 460. The chemical composition then flows into the chemicalcontaining unit 300 via inlet 320. It is understood that the system 100may be configured such that the chemical composition flows directly fromthe dosing unit reservoir 400 to inlet 320 of chemical containing unitvia conduit 420.

As best shown in FIG. 4, this embodiment 100 of the inventive systemincludes all the components illustrated in FIG. 2, except that fourchemical containing units 300 a-d and associated inlets 320 a-d andoutlets 330 a-d along with associated communication links 250 a-d arepresent. The benefits of implementing the invention with a plurality ofchemical containing units is that such a centralized system helps toconsistently maintain a chemical compositions having substantially thesame properties at each of the chemical containing units even if theyare running at different production capacities. In addition, one onlinemonitor may be used for monitoring the bath composition for many tools,thereby reducing cost of ownership. Also, since the monitor and dosingunit is advantageously located in a separate location from the chemicalcontaining units, chemical exchange and chemical handling are notperformed in the location in which the material treatment processoccurs. If the invention is implemented in management of electroplatingbath solutions of wafer-plating tools in semiconductor fabs orfoundries, the dosing unit and monitor may be located in the sub-fabroom or chemical room, rather than the cleanroom area of the fab. Thus,less handling is done in the cleanroom thereby lessening the risk ofcontamination. In addition, there is a potentially smaller footprint inthe cleanroom.

As best shown in FIG. 3, another preferred embodiment 100 of the systemincludes the same components illustrated in FIG. 2, except that fourchemical containing units 300 a-d, associated with inlets 320 a-d,outlets 330 a-d, and communication links 250 a-d are used, and itfurther includes a second monitor 850 associated with a communicationlink 245 between the monitor 850 and controller 200, a chemicalcontaining unit outlet reservoir 350, and a pump 360. Operation of thisembodiment allows control over the quality of multiple chemicalcontaining units, such as four chemical containing units 300 a-d, in acentralized scheme.

In this embodiment, monitor 850 monitors a property of the chemicalcomposition at reservoir 350 via piping 860 and returns it to reservoir350 via piping 870. This embodiment is especially advantageous when themonitor 800, dosing unit reservoir 400 and dosage element 450 arelocated far from the chemical containing units 300 a-d. For example,when the invention is implemented for management of electroplating bathsof wafer-plating tools, the chemical containing units 300 a-d (in thiscase wafer-plating tools) are located in the fab and the dosing unitreservoir 400, dosage element 450, and monitor 800 are located in thesub-fab room. Whether or not the invention is applied to management ofthese baths, the following situation occurs. For a given plug ofchemical composition flow, monitoring of a property by monitor 850 andmonitor 800 may result in different measurements due to the lag time ofthe plug's flow between reservoir 350 and dosing unit reservoir 400. Inorder to help compensate for this difference, monitor 850 and monitor800 together provide signals to controller 200 regarding the monitoredproperty via communication links 245 and 240. Based upon these signals,the controller 200 will implement the best decision regarding theaddition of one or more additives to the chemical composition. Also, ifmonitor 800 detects potential contamination of the chemical composition,selected valves isolating the chemical composition in the chemicaltreatment units and associated piping and the dosing unit may be shutdown so as to not contaminate the whole system.

A preferred embodiment of the dosage element 450 is best illustrated inFIG. 5. During a period in which the additives are not being added tothe chemical composition, flow of the composition to dosage element 450via piping 425 does not ordinarily occur (by action of closed valves notshown). When the controller 200 sends a signal to the dosage element tobegin dosing the additives to the composition, pump 415 is activated andthe composition flows to dosage element 450 via piping 425 into conduit426. Addition to the chemical composition of additive from additivecontainer 480 a is described below.

At the moment that dosage element 450 receives a signal from thecontroller 200 to begin dosing the additive from container 480 a, aflushing cycle is initiated. In the flushing cycle, valve 471 is opened.This operation lasts for a specified time in order to flush the contentsof the line from valve 471 to valve 473. After the flush has beencompleted, the pump is deactivated, and valves 473, 471 are closed. Thedosing element 450 receives another signal from the controller 200 tobegin dosing the additive from container 480 a, the three way valve 428a is opened, the pump 472 is activated, and valve 473 is opened. At thispoint, the upstream portion of three-way valve 428 a is closed while theother two portions are open. Also the in-line portions of valves 428 b,428 c and 428 d are opened while the remaining portions of these valvesadjacent conduits 429 b, 429 c and 429 d remain closed. By action ofpump 472, the additive from container 480 a flows through conduit 429 aand past conduit 427 b, open three-way valve 428 b, conduit 427 c, openthree-way valve 428 c, conduit 427 d, open three-way valve 428 d, andinto conduit 427 e past pump 472. The amount of the additive ispreferably controlled by one of two methods. The flow rate at flow meter474 is monitored during the flushing cycle and then integrated overtime, thereby yielding a relationship between the volume of flow pastthe pump 472 and the time during which the pump 472 is activated. Basedupon this time/flow relationship, the amount of time which pump 472 isactivated during the dosing determines the volume of additive added.

When the selected amount of additive from container 480 a is determinedto be introduced into conduit 427 b or downstream thereof, the upstreamand downstream portions of three-way valve 428 a adjacent conduits 427 aand 427 b are opened and the remaining portion adjacent conduit 429 a isclosed. Substantially simultaneously, valve 471 is opened and by actionof pumps 472 and 415, the chemical composition flows into conduit 427 avia conduit 426 and piping 425. The in-line portions of three-way valves428 b, 428 c and 428 d are open, thereby allowing the chemicalcomposition to flow through conduits 427 b, 427 c, 427 d, 427 e, andvalve 473. The chemical composition then enters conduit 431 where it isdirected to piping 430 via pump 415 and into the dosing unit reservoir400. If the controller 200 indicates that no other additive should bedosed, once a selected amount of chemical composition has flowed throughthis loop of conduits parallel conduit 426, valves 471 and 473 areclosed and pumps 472 and 415 shut down. At this point, flow of thechemical composition between dosing unit reservoir 400 and dosageelement 450 is interrupted.

Those skilled in the art will understand that addition of any other ofthe additives from containers 480 b, 480 c or 480 d may be achieved inthe same manner with the addition and flushing sequences as describedabove.

A preferred embodiment of chemical delivery unit 110 is best illustratedin FIG. 6. Chemical composition flows into day tank 160 via eitherconduits 150 or 420. The chemical composition flows out of day tank 160through conduit 161 and into pressure-feed vessel 120 a, while at thesame time chemical composition flows out of pressure-feed vessels 120 band into conduit 460 by action of blanket gas system 130. Flow ofchemical composition through conduit 161 and into or out of pressurefeed vessels 120 a and b is achieved by known arrangements of valving inorder to avoid mixing the two flows. When a sensor in pressure-feedvessel 120 a senses a high liquid level and a sensor in pressure-feedvessel 120 b senses a low liquid level, flow of the chemical compositionthereinto is interrupted, while at the same time, flow out ofpressure-feed vessel 120 b is also interrupted. At this point, thefilling and emptying of the two pressure-feed vessels 120 a, b isswitched, i.e., pressure-feed vessel 120 a is emptied by flow ofchemical composition out of it and into conduit 460 by blanket gassystem 130, while pressure-feed vessel 120 b is being filled.

Pressure sensors may be used to determine the beginning and end of afill or empty cycle as described above instead of liquid level sensors.

The online monitor 800 may be any online monitor known to thoseordinarily skilled in the art suitable for use in the invention. Apreferred online monitor is a “real-time analyzer”, RTA, available fromTechnic, Inc, Cranston, in R.I., U.S.A. Another monitor suitable for usein the invention is the ECI system available from ATMI, Danbury, Conn.,U.S.A.

Optionally and in some situations, based upon a signal from onlinemonitor 800, the controller 200 determines that the flow of chemicalcomposition should bypass the dosing unit reservoir 400. This situationis especially desirable when the controller 200 determines that the oneor more additives should be added to the chemical composition at dosingunit reservoir 400 by dosage element 450.

The above bypass is implemented in the following manner. Controller 200determines whether or not to allow the flow of chemical composition tobypass the dosing unit reservoir 400. A signal based upon thisdetermination is sent from controller 200 to valves 151 and 152 viacommunication links 251 and 252 to allow the valves to remain open,remain closed, open from a closed position, or close from an openposition. When chemical composition is flowing from chemical containingunit 300 to dosing unit reservoir 400 via outlet 330 and conduit 140, adecision by the controller 200 to allow the chemical composition tobypass these components results in a signal from controller 200 to closevalve 151 and open valve 152. The chemical composition then leavesconduit 140, enters conduit 150 and flows to chemical delivery unit 110.In this instance, pump 440 is actuated such that the flow of chemicalcomposition from dosing unit reservoir 400 to the optional chemicaldelivery unit is interrupted. Actuation of the pump 440 is preferablycontrolled by the controller 200 at the same time the bypass isimplemented. Otherwise, the pump 440 could be damaged.

As described above, the flow of chemical composition may optionally beallowed to bypass the dosing unit reservoir 400 because the controller200 determines that one or more additives should be added to thechemical composition. In this instance and contemporaneously with thebypass of the flow of chemical composition via conduit 150 as describedabove, a flow of chemical composition to and from the dosing unitreservoir 400 and dosage element 450 via piping 425 and 430 occurs. Theone or more additives are then added to the chemical composition bydosage element 450 as described above. When addition to the chemicalcomposition of the one or more additives is completed and the combinedchemical composition and additives enter the dosing unit reservoir 400,controller 200 sends signals to valve 151 to open and valve 152 toclose, thereby allowing the chemical composition to flow from chemicalcontaining unit 300 to dosing unit reservoir 400.

Preferably, when one or more additives are being added to the chemicalcomposition by dosage element 450, an otherwise interrupted flow ofchemical composition from/to the dosing unit reservoir 400/dosageelement 450 via piping 425 and 430 is allowed to commence. This mayoccur by actuation of one or more valves to close and operation of oneor more pumps to be interrupted. At the same time, the chemicalcomposition from chemical containing unit 300 bypasses dosing unitreservoir 400 as described above.

Also preferably, when addition to the chemical composition of the one ormore additives is completed, the flow of chemical composition from/tothe dosing unit reservoir 400/dosage element 450 via piping 425 and 430ceases. At the same time, controller 200 sends signals to valve 151 toopen and valve 152 to close, thereby allowing the chemical compositionto flow from chemical containing unit 300 to dosing unit reservoir 400.

It should be understood that valves 151, 152 could be electric solenoidor pneumatic valves. In the case of electric solenoid valves actuationof valves 151, 152 is performed as described above, i.e., by the sendingof a signal from controller 200. However, it should be also beunderstood that in the case of pneumatic valves, they need not beactuated directly by controller 200 via signals along communicationlinks 251, 252. For example, the controller may send a signal to asource of compressed air which then pressurizes a pneumatic line whichultimately opens or closes a pneumatic valve. The source of compressedmay be located adjacent the controller 200, at the valve 151, 152, orany point therebetween. For that matter, any pneumatic valve or pump maybe controlled by controller 200 in this manner.

In these above preferred situations, two modes of chemical compositionflow are described. When no addition of one or more additives to thechemical composition occurs, a main recirculation mode is present andthe chemical composition is allowed to flow from the chemical containingunit 300 to the dosing unit reservoir 400 and thenceforth to optionalchemical delivery unit 110 via conduit 420 and optional conduit 46 tochemical containing unit 300. This flow is referred to as loop C.

When addition of one or more additives to the chemical composition doesoccur, a dosing mode is present and the chemical composition flows fromthe chemical containing unit 300 through outlet 330, conduit 150 tochemical delivery unit 110 and thence forth to the chemical containingunit 300 via conduit 460 and inlet 320. This flow is referred to as loopA. In the same mode and at the same time, the chemical composition flowsfrom/to the dosing unit reservoir 400/dosage element 450 via piping 425and 430. This flow is referred to as loop B. The benefits of such atwo-mode system are that solution recirculation feeding the chemicalcontaining unit (or wafer-coating tool if the invention is implementedin management of electroplating bath solutions) can still be done whiledosing inside the dosing unit is occurring. Thus continuous chemicaldelivery is achieved.

Predictive Corrective Controller

While any one of the closed-loop control schemes known in the art may beused with controllers 65, 200, the inventors have invented aparticularly advantageous control solution that overcomes thedisadvantages presented by the prior art. The solution is a controlsystem (programmable logic controller (PLC), Industrial PC or alike)suitably programmed with a closed loop feedback dosing algorithm thatutilizes actual process concentration data to correct for consumption ofcritical components in the chemical composition. It may also provide apredicted dosing volume in-between actual concentration data times, ifthe later are too large. It may also correct the dose when an actualvalue becomes available. It maintains the levels of one or moreadditives within a desired range by specifying amounts of additivesand/or fresh chemical composition to be added to the chemicalcomposition, as well as specifying when preset volumes of chemicalcomposition should be bled from the system.

The algorithm has several advantages. It is substantially independent ofany changes in the kinetics of the chemical composition constituents,such as consumption rates, production mode, as well as independent ofprocess tool specificities. It is also substantially independent ofchanges in the chemical composition's chemistry, such as variance ofbulk chemical supplies, acidity, etc. Also, it is not dependent upon anyone type of online monitor. Additionally, it is also scalable and thusable to support multiple chemical composition management configurations.Furthermore, the dosing frequency is tunable and dosing could take placeeven if actual process concentration data are not continuouslyavailable. In other words, addition of one or more additives may be madein between actual measurements of one or more properties by a monitor.Finally, the controller is robust enough to tolerate variable bathbleeding rates and typical process disturbances, such as addition ofdeionized water.

Due to the long sampling time of current online analyzers, the algorithmwill predict concentrations at a desired frequency, also known as thedosing frequency. Each set of data either monitored or predicted isinspected by a diagnostic function to determine whether the operatingmode of the system should be switched from the main recirculation modeto the dosing mode. If addition of one or more additives is determinedby the algorithm as necessary, the controller will put the system in thedosing mode. As a result, the flow through loop C will be interruptedand flows through loops A and B commenced.

The algorithm will compute additive and fresh chemical compositionvolumes to bring all chemical composition concentrations of interestback to setpoint values. The calculated volumes are introduced into thesystem as described above. When the chemical composition and additivesare deemed to be suitably mixed, the system is switched back from thedosing mode to the main recirculation mode and flow through loop Cresumed.

In the absence of any control, the additive concentrations in thechemical composition will naturally deplete as a result of the ongoingmaterial treatment process. If no action is taken, such concentrationswill eventually cross below a threshold resulting in improper materialtreatment. In the case of electroplating bath solutions forwafer-coating, such phenomena as unacceptable metal deposition andformation of voids may occur.

For each additive, the dosing aims to re-establish target concentrationin the solution. At time t, flows of the chemical composition throughloops A and B commence. The concentration in the chemical containingunit will continue to decrease at rate r(t) due to the on-going materialtreatment process. The dosing is performed in the dosing unit by addinga volume V_(dosed)(t) of nominal additive at time t. Such a volume willmake the system's additive concentration within a predeterminedconcentration range around the setpoint when the recirculation modecommences again at time t+Δt.

Various aspects of the predictive corrective algorithm are now describedas follows. TABLE IV Nomenclature Component Symbol Continuous DiscreteTime Time Description V_(PT) Chemical containing unit volume V_(BT)Dosing unit reservoir volume V_(dosed)(t) V_(i) Volume Dosed at time tor t_(i) V_(bleed)(t) = α(t) · V_(BT) α_(i) · V_(BT) Volume Bled at timet or t_(i) C₀ Target concentration in chemical containing unit{overscore (C)} Nominal concentration of chemical additive t t_(i) Timethe dosing is started or i^(th) dosing time θ_(RTA) Monitor time delay$f_{s} = \frac{1}{\theta_{RTA}}$ Monitor sampling frequencyΔt = N ⋅ θ_(RTA), N ∈ {1, 2, …  } Δt = t_(i+1) − t_(i) Dosing period$f_{d} = \frac{1}{\Delta t}$ Dosing frequency C_(PT)(t) C_(i,PT)Concentration in chemical containing unit at time t or t_(i) C_(PT)(t +Δt) C_(i+1),PT Concentration in chemical containing unit at time t + Δtor t_(i+1) C_(BT)(t) C_(i,BT) Concentration in dosing unit reservoir attime t or t_(i) C(t) C_(i) Concentration in chemical containing unit ordosing unit reservoir at time t or t_(i)${r(t)} = {{\overset{.}{C}(t)} = \frac{\mathbb{d}C}{\mathbb{d}t}}$$r_{i} = {\overset{.}{C}}_{i}$ Chemical Consumption Rate at time t ort_(i) ${\delta(t)} = {{\overset{¨}{C}(t)} = \frac{d^{2}C}{{dt}^{2}}}$$\delta_{i} = {\overset{¨}{C}}_{i\quad}$ Consumption Rate variation attime t or t_(i) {circumflex over (X)}(t) {circumflex over (X)}_(i)Estimated value of physical quantity X (C, r, . . . etc) at time t ort_(i)

TABLE VI Assumptions Assumption Continuous Time Discrete Time 1 Perfectmixing C_(PT)(t) = C_(BT)(t) = C(t) C_(i,PT) = C_(i,BT) = C_(i) duringrecirculation 2 Dosing reservoir is C_(BT)(t) = C_(BT)(t + Δt) C_(i,BT)= C_(i+1),BT reaction free: 3 Constant Consumption Rate over θ_(RTA):$\begin{matrix}{{{r( {t - {\Delta t}} )} = {{r( {t - \theta_{RTA}} )}{\forall{{\Delta t} \in \lbrack {0,\theta_{RTA}} \rbrack}}}}\quad} \\{{C_{PT}(t)} = {{\int_{t - {\Delta t}}^{t}{{r( {t - {\Delta t}} )}{\mathbb{d}x}}} + {C_{PT}( {t - {\Delta t}} )}}} \\{\quad{= {{{r( {t - \theta_{RTA}} )}{\Delta t}} + {C_{PT}( {t - {\Delta t}} )}}}}\end{matrix}\quad$ C_(i,PT) = r_(i−1)Δt + C_(i−1,PT) 4 ConstantConsumption Rate variation over 2θ_(RTA): ${\begin{matrix}{{{\delta( {t - {\Delta t}} )} = {{\delta( {t - {2\theta_{RTA}}} )}{\forall{{\Delta t} \in \lbrack {0,\theta_{RTA}} \rbrack}}}}\quad} \\{{{r(t)} = {{\int_{t - {\Delta t}}^{t}{{\delta( {t - {\Delta t}} )}{\mathbb{d}x}}} + {r( {t - {\Delta t}} )}}}\quad} \\{\quad{= {{2{\delta( {t - {2\theta_{RTA}}} )}{\Delta t}} + {r( {t - {\Delta t}} )}}}}\end{matrix}\quad}\quad$ r_(i) = δ_(i−1)Δt + r_(i−1)1. Dosing Algorithm for Single Component Case:a) Continuous-Time Single Component Dosing (CTSC)

In one preferred embodiment, dosing is performed in the dosing unitreservoir 400 by adding a volume V_(dosed)(t) of nominal solution attime t. Such volume will make the system's concentration reach itstarget value at time t+Δt. This statement translates into the followingequation:(Mass in System at t+Δt)=(Mass in dosing unit reservoir at t)+(Massadded into dosing unit reservoir at t)+(Mass in chemical containing unitat t+Δt)−(Mass bled off the System at t)  Eq. 1 $\begin{matrix}\begin{matrix}{{C_{0} \cdot ( {V_{BT} + V_{PT} + {V_{dosed}(t)}} )} = {{{C_{BT}(t)} \cdot V_{BT}} + {\overset{\_}{C} \cdot {V_{dosed}(t)}} +}} \\{{{C_{PT}( {t + {\Delta\quad t}} )} \cdot V_{PT}} - {{V_{bleed}(t)} \cdot {C(t)}}} \\{= {{( {1 - {\alpha(t)}} ) \cdot {C(t)} \cdot V_{BT}} + {\overset{\_}{C} \cdot}}} \\{{V_{dosed}(t)} + {{C( {t + {\Delta\quad t}} )} \cdot V_{PT}}}\end{matrix} & {{Eq}.\quad 2}\end{matrix}$V_(dosed)(t) may be solved: $\begin{matrix}{{V_{dosed}(t)} = \frac{{\lbrack {C_{0} - {( {1 - {\alpha(t)}} ) \cdot {C(t)}}} \rbrack \cdot V_{BT}} + {\lbrack {C_{0} - {C( {t + {\Delta\quad t}} )}} \rbrack \cdot V_{PT}}}{\overset{\_}{C} - C_{0}}} & {{Eq}.\quad 3}\end{matrix}$

In the previous expression the concentrations at time t and at time t+Δtare unknown. It takes θ_(RtA) for the monitor to generate one set ofresults. Only C (t−θ_(RTA)) and the previous rate are available throughthe monitor 800 and/or direct computation respectively. Using assumption3, one can estimate the concentration at time t:Ĉ(t)=r(t−Δt)Δt+C(t−Δt)  Eq. 4

Furthermore, the concentration at the end of the dosing period i.e. att+Δt is not known. The consumption rate is not necessarily constant fromone sampling period to the next. However, using assumption 4, one canestimate the consumption rate:{circumflex over (r)}(t)=δ(t−Δt)Δt+r(t−Δt)  Eq. 5

Thus, the estimated concentration at t+Δt using Eq. 4 and Eq. 5 is:$\begin{matrix}\begin{matrix}{{\hat{C}( {t + {\Delta\quad t}} )} = {{{{\hat{r}(t)}\Delta\quad t} + {\hat{C}(t)}} = {\lbrack {{{\delta( {t - {\Delta\quad t}} )}\Delta\quad t} + {r( {t - {\Delta\quad t}} )}} \rbrack \cdot}}} \\{{\Delta\quad t} + {{r( {t - {\Delta\quad t}} )}\Delta\quad t} + {C( {t - {\Delta\quad t}} )}} \\{= {{{\delta( {t - {\Delta\quad t}} )}( {\Delta\quad t} )^{2}} + {2{r( {t - {\Delta\quad t}} )}\Delta\quad t} +}} \\{C( {t - {\Delta\quad t}} )}\end{matrix} & {{Eq}.\quad 6}\end{matrix}$

Eq. 3 may be rewritten by replacing the concentration at time t [C(t)]and consumption rate [{circumflex over (r)}(t)] by their estimatedvalues in Eq. 4 and in Eq. 6 respectively to determine the volume to bedosed into the system: $\begin{matrix}{{{\hat{V}}_{dosed}(t)} = \frac{\begin{matrix}{{\{ {C_{0} - {( {1 - {\alpha(t)}} ) \cdot \lbrack {{{r( {t - {\Delta\quad t}} )}\Delta\quad t} + {C( {t - {\Delta\quad t}} )}} \rbrack}} \} \cdot V_{BT}} +} \\{\{ {C_{0} - \lfloor {{{\delta( {t - {\Delta\quad t}} )}( {\Delta\quad t} )^{2}} + {2{r( {t - {\Delta\quad t}} )}\Delta\quad t} + {C( {t - {\Delta\quad t}} )}} \rfloor} \} \cdot V_{PT}}\end{matrix}}{\overset{\_}{C} - C_{0}}} & {{Eq}.\quad 7}\end{matrix}$b) Discrete Time Single Component (DTSC) Dosing Algorithm:

In another preferred embodiment, the CTSC dosing algorithm utilizes adiscrete time controller to control the chemical compositionconcentration. Like in the continuous case, the volume V_(i) of nominalsolution at time t_(i) will make the system's concentration reach itstarget value when the blending tank unit 400 is interfaced at timet_(i+1). This statement translates into the following equation:(Mass in System at t _(i+1))=(Mass in dosing unit reservoir at t_(i))+(Mass added to dosing unit reservoir at t _(i))+(Mass in chemicalcontaining unit at t _(i+1))−(Mass bled off the System at t _(i))  Eq.1′C ₀·(V _(BT) +V _(PT) +V _(i))=C _(i) ·V _(BT) +{overscore (C)}·V _(i)+C _(i+1) ·V _(PT) −α _(i) ·V _(BT) ·C _(i)  Eq. 2′

V_(i) may be solved: $\begin{matrix}{V_{i} = \frac{{\lbrack {C_{0} - {( {1 - \alpha_{i}} ) \cdot C_{i}}} \rbrack \cdot V_{BT}} + {\lbrack {C_{0} - C_{i + 1}} \rbrack \cdot V_{PT}}}{\overset{\_}{C} - C_{0}}} & {{Eq}.\quad 3^{\prime}}\end{matrix}$

The concentrations C_(i) and C_(i+1) are unknown. Using assumption 3,one can estimate the concentration at time t_(i): $\begin{matrix}{{\hat{C}}_{i} = {{{r_{i - 1}\Delta\quad t} + C_{i - 1}} = {{\sum\limits_{k = 0}^{i - 1}{r_{k}\Delta\quad t}} + C_{0}}}} & {{Eq}.\quad 4^{\prime}}\end{matrix}$

Using assumption 4, one can estimate the consumption rate:$\begin{matrix}{{\hat{r}}_{i} = {{{\delta_{i - 1}\Delta\quad t} + r_{i - 1}} = {{\sum\limits_{k = 0}^{i - 1}{\delta_{k}\Delta\quad t}} + r_{0}}}} & {{Eq}.\quad 5^{\prime}}\end{matrix}$

The estimated concentration at t_(i+1) using Eq. 4′ and Eq. 5′ is:$\begin{matrix}{{\hat{C}}_{i + 1} = {{( {{\sum\limits_{k = 0}^{i - 1}{\delta_{k}\Delta\quad t}} + r_{0}} )\Delta\quad t} + {\sum\limits_{k = 0}^{i - 1}{r_{k}\Delta\quad t}} + C_{0}}} & {{Eq}.\quad 6^{\prime}}\end{matrix}$

Eq. 3′ may be rewritten using Eq. 4′ and Eq. 6′ to determine the volumeto be dosed into the system: $\begin{matrix}{{\hat{V}}_{i} = \frac{\begin{matrix}{{( {{\alpha_{i} \cdot C_{0}} - {( {1 - \alpha_{i}} ) \cdot {\sum\limits_{k = 0}^{i - 1}{r_{k}\Delta\quad t}}}} )V_{BT}} +} \\{( {{\sum\limits_{k = 0}^{i - 1}{\delta_{k}\Delta\quad t}} + r_{0} + {\sum\limits_{k = 0}^{i - 1}r_{k}}} )\Delta\quad{t \cdot V_{PT}}}\end{matrix}}{C_{0} - \overset{\_}{C}}} & {{Eq}.\quad 7^{\prime}}\end{matrix}$2. Dosing Algorithm for Multi-Component Case:a) Discrete Time Multi-Component (DTMC) Dosing Algorithm:

In another preferred embodiment, multiple components are controlledusing a discrete time algorithm in the controller 200. Like in thesingle component case, the volume V_(i,j) of Component j nominalsolution at time t_(i) will make the system's j^(th) concentration reachits target value when the dosing unit reservoir 400 is circulated backto the chemical containing unit 300 at time t_(i+1). This statementtranslates into the following equation:(Mass of j ^(th) Component in System at t _(i+1))=(Mass of j ^(th)Component in dosing unit reservoir at t _(i))+(Mass of j ^(th) Componentadded to dosing unit reservoir at t _(i))+(Mass of j ^(th) Component in chemical containing unit at t_(i+1))−(Mass of j ^(th) Component bled off the System at t _(i))  Eq.1″ $\begin{matrix}{{{C_{0,j} \cdot ( {V_{BT} + V_{PT} + {\sum\limits_{k = 1}^{n}V_{i,k}}} )} = {{C_{i,j} \cdot V_{BT}} + {\overset{\_}{C_{j}} \cdot V_{i,j}} + {C_{{i + 1},j} \cdot V_{PT}} - {\alpha_{i} \cdot V_{BT} \cdot C_{i,j}}}}\quad{j \in \lbrack {1,n} \rbrack}} & {{Eq}.\quad 2^{''}}\end{matrix}$ ${{{Let}\quad C_{i}} = \begin{bmatrix}C_{i,1} \\\ldots \\C_{i,j} \\\ldots \\C_{i,n}\end{bmatrix}},{V_{i} = {\begin{bmatrix}V_{i,1} \\\ldots \\V_{i,j} \\\ldots \\V_{i,n}\end{bmatrix}\quad{and}}}$ $A = \begin{bmatrix}( {C_{0,1} - {\overset{\_}{C}}_{1}} ) & C_{0,1} & \ldots & \ldots & C_{0,1} \\\ldots & \ldots & \ldots & \ldots & \ldots \\C_{0,j} & \ldots & ( {C_{0,j} - {\overset{\_}{C}}_{j}} ) & \ldots & C_{0,j} \\\ldots & \ldots & \ldots & \ldots & \ldots \\C_{0,n} & \ldots & \ldots & C_{0,n} & ( {C_{0,n} - {\overset{\_}{C}}_{n}} )\end{bmatrix}$

Using the above notations, Eq. 2″ becomes:V _(i) =A ⁻¹·[((1−α_(i))·C_(i) −C ₀)·V _(BT)+(C _(i+1) −C ₀)·V_(PT])  Eq. 3″

In the previous expression the concentration vectors C_(i) and C_(i+1)are unknown but can be estimated. If $r_{i} = \begin{bmatrix}r_{i,1} \\\ldots \\r_{i,j} \\\ldots \\r_{i,n}\end{bmatrix}$is the rate vector, then the current (i.e. at time t_(i)) concentrationvector: $\begin{matrix}{{\hat{C}}_{i} = {{{r_{i - 1}\Delta\quad t} + C_{i - 1}} = {{\sum\limits_{k = 0}^{i - 1}{r_{k}\Delta\quad t}} + C_{0}}}} & {{Eq}.\quad 4^{''}}\end{matrix}$

Like in the single component case, one can estimate the currentconsumption rate vector: $\begin{matrix}{{\hat{r}}_{i} = {{{\delta_{i - 1}\Delta\quad t} + r_{i - 1}} = {{\sum\limits_{k = 0}^{i - 1}{\delta_{k}\Delta\quad t}} + r_{0}}}} & {{Eq}.\quad 5^{''}}\end{matrix}$

The concentration vector may be estimated at t_(i+1) using Eq. 4″ andEq. 5″: $\begin{matrix}{{\hat{C}}_{i + 1} = {{( {{\sum\limits_{k = 0}^{i - 1}{\delta_{k}\Delta\quad t}} + r_{0}} )\Delta\quad t} + {\sum\limits_{k = 0}^{i - 1}{r_{k}\Delta\quad t}} + C_{0}}} & {{Eq}.\quad 6^{''}}\end{matrix}$

Eq. 3″ may be rewritten using Eq. 4″ and Eq. 6″ to determine the volumeto be dosed into the system: $\begin{matrix}\begin{matrix}{{\hat{V}}_{i} = {A^{- 1} \cdot \lbrack {{( {{( {1 - \alpha_{i}} ) \cdot {\sum\limits_{k = 0}^{i - 1}{r_{k}\Delta\quad t}}} - {\alpha_{i} \cdot C_{0}}} )V_{BT}} +} }} \\ {( {{\sum\limits_{k = 0}^{i - 1}{\delta_{k}\Delta\quad t}} + r_{0} + {\sum\limits_{k = 0}^{i - 1}r_{k}}} )\Delta\quad{t \cdot V_{PT}}} \rbrack\end{matrix} & {{Eq}.\quad 7^{''}}\end{matrix}$b) Corrected Discrete Time Multi-Component (CDTMC) Dosing Algorithm:

In another preferred embodiment, a monitor is used to correct the DTMCdosing volume. The monitor utilized for concentration measurements canhave a significant dead time θ_(RTA). In other words:$\quad\{ \begin{matrix}{{{{C_{measured}(t)} = {C_{actual}( {t - \theta_{RTA}} )}},\quad{0 \leq t < \infty}}\quad} \\{{{{C_{measured}(t)} = 0},\quad{t < 0}}\quad}\end{matrix} $

The monitor transfer function in the s-domain (frequency domain) isC_(measured)(s)=e^(−sθ) ^(RTA) ·C_(actual)(s). However, this formulationis impractical as the actual concentration is being sampled. Therefore,a discrete time representation in the z-domain may be utilized:C _(i,measured) =Z ^(−θ) ^(RTA) ·C _(i,actual) where z=e ^(sθ) ^(RTA)meaning thatC _(i,j) ^(measured) =z ^(−θ) ^(RTA) ·C _(i,j) ^(actual) =C _(i−1) ,j^(measured).

Due to the monitor dead time, C_(i) is available at t_(i+1) and C_(i+1)at t_(i+2). Therefore at t_(i+2), one must correct the dosed volumecalculated based on the reading at time t_(i). The error of the dosedvolume of the j^(th) at t_(i−2) is defined and corrected at t_(i) asfollows: $\begin{matrix}\{ \begin{matrix}{{ɛ_{i,j} = {{\lambda_{j} \cdot ( {V_{{i - 2},j} - {\hat{V}}_{{i - 2},j}} )} + {( {1 - \lambda_{j}} ) \cdot ɛ_{{i - 1},j}}}},\quad{i \geq 2}} \\{\quad{ɛ_{1,j} = {ɛ_{0,j} = 0}}\quad}\end{matrix}  & {{Eq}.\quad 8^{''}}\end{matrix}$

This exponentially weighted moving average error is either positive ornegative. To demonstrate that the error ε_(i,j) is a weighted average ofall the previous deviations of the estimated volume from the real dosedvolume, recursively for ε_(i−k,j) is substituted recursively:$\quad\begin{matrix}\{ \begin{matrix}{{ɛ_{i,j} = {{\lambda_{j} \cdot {\sum\limits_{k = 2}^{i}{( {1 - \lambda_{j}} )^{i - k} \cdot ( {V_{{k - 2},j} - {\hat{V}}_{{k - 2},j}} )}}} + {( {1 - \lambda_{j}} )^{i - 1} \cdot ɛ_{1,j}}}},{i \geq 2}} \\{{ɛ_{1,j} = {ɛ_{0,j} = 0}}\quad}\end{matrix}  & {{Eq}.\quad 9^{''}}\end{matrix}$

The weights$\lambda_{j} \cdot {\sum\limits_{k = 2}^{i}( {1 - \lambda_{j}} )^{i - k}}$decrease geometrically with the age of the error.

Furthermore, the weights sum to unity, since: $\begin{matrix}{{\lambda_{j} \cdot {\sum\limits_{k = 2}^{i}( {1 - \lambda_{j}} )^{i - k}}} = {{\lambda_{j} \cdot {\sum\limits_{k = 0}^{i - 2}( {1 - \lambda_{j}} )^{k}}} = {{\lambda_{j} \cdot \frac{1 - ( {1 - \lambda_{j}} )^{i - 3}}{1 - ( {1 - \lambda_{j}} )}} = {1 - ( {1 - \lambda_{j}} )^{i - 3}}}}} & {{Eq}.\quad 10^{''}}\end{matrix}$

Let $\lambda = \begin{bmatrix}\lambda_{1} & 0 & \cdots & \cdots & 0 \\0 & \cdots & \cdots & \cdots & \cdots \\\cdots & \cdots & \lambda_{j} & \cdots & \cdots \\\cdots & \cdots & \cdots & \cdots & 0 \\0 & \cdots & \cdots & 0 & \lambda_{n}\end{bmatrix}$the diagonal matrix of the weights of each componentand $ɛ_{i} = {\begin{bmatrix}ɛ_{i,1} \\\cdots \\ɛ_{i,j} \\\cdots \\ɛ_{i,n}\end{bmatrix}.}$

Using the above notations, Eq. 8″ becomes: $\begin{matrix}\{ \begin{matrix}{{ɛ_{i} = {{\lambda \cdot ( {V_{i - 2} - {\hat{V}}_{i - 2}} )} + {( {I - \lambda} ) \cdot ɛ_{i - 1}}}},{i \geq 2}} \\{ɛ_{0} = {ɛ_{1} = 0}}\end{matrix}  & {{Eq}.\quad 11^{''}}\end{matrix}$

ε_(i−k) is recursively substituted: $\quad\begin{matrix}\{ \begin{matrix}{{ɛ_{i} = {{\sum\limits_{k = 2}^{i}{( {I - \lambda} )^{i - k} \cdot \lambda \cdot ( {V_{k - 2} - {\hat{V}}_{k - 2}} )}} + {( {I - \lambda} )^{i - 1} \cdot ɛ_{1}}}},{i \geq 2}} \\{ɛ_{0} = {ɛ_{1} = 0}}\end{matrix}  & {{Eq}.\quad 12^{''}}\end{matrix}$

Thus, the corrected volume at time t_(i) can be calculated as follows:$\begin{matrix}{{\hat{V}}_{i} = {{A^{- 1} \cdot \lbrack {{( {{( {1 - \alpha_{i}} ) \cdot {\sum\limits_{k = 0}^{i - 1}{r_{k}\Delta\quad t}}} - {\alpha_{i} \cdot {\mathbb{C}}_{0}}} )V_{BT}} + {( {{\sum\limits_{k = 0}^{i - 1}{\delta_{k}\Delta\quad t}} + r_{0} + {\sum\limits_{k = 0}^{i - 1}r_{k}}} )\Delta\quad{t \cdot V_{PT}}}} \rbrack} \pm {ɛ_{i}}}} & {{Eq}.\quad 13^{''}}\end{matrix}$

In equation 13″, absolute value of error is added when under dosingoccurred at previous time step, otherwise value of error is subtractedwhen over dosing occurred at previous time step.

As seen above, the algorithm determines a rate of depletion over adepletion time period of at least one of the additives in the chemicalcomposition based upon a concentration of the additive measured by themonitor in comparison to a concentration of the additive previouslymeasured by the monitor. The algorithm also predicts an amount of atleast one additive that when added to the chemical composition willmaintain a concentration of the additive within a predeterminedconcentration range around a predetermined setpoint concentration. Thealgorithm also corrects the predicted amount by adding to, orsubtracting from, the predicted amount, an amount of the additive basedupon previous concentrations of the additive measured by the monitor.The corrected amount is the dose added to the chemical composition bythe dosage element.

In contrast to prior art controllers, the algorithm has the followingadditional novel features. The amount added to or subtracted from thepredicted amount is based upon at least two previous measurements by themonitor of the concentration of the at least one additive. Also, thetime interval between additions of the at least one additive is lessthan a time interval between measurements by said monitor. Furthermore,the time interval in between additions is also tunable, i.e., it may bevaried to any interval no less than the time it takes the dosage elementto add the at least one additive. Moreover, the predicted amount is alsobased upon a derivative of the depletion rate. Finally, the predictedamount does not depend upon a variable condition at said chemicalcontaining unit.

Having described novel systems and methods for monitoring, dosing anddistribution of chemical compositions in material treatment processes,it is believed that other modifications, variations and changes will besuggested to those skilled in the art in view of the teachings set forthherein. It is therefore to be understood that all such variations,modifications and changes are believed to fall within the scope of theclaims.

1. A system for monitoring, dosing and distribution of a chemicalcomposition in a material treatment process, the chemical compositioncontaining at least one additive for maintaining quality of the chemicaltreatment process, said system comprising: at least one chemicalcontaining unit configured to contain the chemical composition for thechemical treatment process; a dosing unit fluidly communicating withsaid at least one chemical containing unit configured to receive thechemical composition therefrom and to add a selected dose of the atleast one additive to the chemical composition therein; a online monitorconfigured to monitor a property of the chemical composition at saiddosing unit and to transmit a signal corresponding to the monitoredproperty; and a controller programmed and configured to receive thesignal from said online monitor and send a signal to said dosing unit toadd the selected dose to the chemical composition therein in response tothe monitored property.
 2. The system of claim 1, wherein the controllercomprises a processor programmed with an algorithm such that theprocessor: determines a rate of depletion over a depletion time periodof at least one of the at least one additive in the chemical compositionbased upon a concentration of the at least one of the at least oneadditive measured by said monitor in comparison to a concentration ofthe at least one of the at least one additive which was last measured bysaid monitor; predicts an amount of the at least one of the at least oneadditive that when added to the chemical composition will maintain aconcentration of the additive within a predetermined concentration rangearound a predetermined setpoint concentration; and corrects thepredicted amount by adding to, or subtracting from, the predictedamount, an amount of the at least one additive based upon a previousmeasurement by said monitor of the concentration of the at least oneadditive, wherein the corrected amount is the selected dose.
 3. Thesystem of claim 1, wherein said at least one chemical containing unit isan electroplating bath of a wafer electroplating tool.
 4. The system ofclaim 2, wherein said at least one chemical containing unit is anelectroplating bath of a wafer electroplating tool.
 5. The system ofclaim 1, further comprising: a chemical delivery unit in fluidcommunication with said at least one chemical containing unit and saiddosing unit and configured to deliver the chemical composition to saidat least one chemical containing unit
 6. The system of claim 5, furthercomprising: a first valve arrangement in fluid communication with saidchemical containing unit and said dosing unit, said first valvearrangement configured to allow or prevent a flow of the chemicalcomposition from said chemical containing unit to said dosing unit; anda second valve arrangement in fluid communication with said chemicalcontaining unit and said chemical delivery unit, said second valvearrangement configured to allow or prevent a flow of the chemicalcomposition from said chemical containing unit to said chemical deliveryunit.
 7. The system of claim 6, wherein said controller comprises aprocessor programmed with an algorithm such that it: determines whethersaid system should operate in a main recirculation mode in which saidfirst valve arrangement allows a flow of the chemical composition fromsaid at least one chemical containing unit to said dosing unit and saidsecond valve arrangement prevents a flow of the chemical compositionfrom said at least one chemical containing unit to said dosing unit, orin a dosing mode in which said first valve arrangement prevents a flowof the chemical composition from said chemical containing unit to saiddosing unit and allows a flow of the chemical composition from said atleast one chemical containing unit to said chemical delivery unit. 8.The system of claim 7, wherein in response to said algorithm determiningthat the system should operate in the main recirculation mode, saidcontroller i) sends a signal to either open said first valve arrangementor to allow said first valve arrangement to remain open so that a flowof the chemical composition is allowed from said at least one chemicalcontaining unit to said dosing unit, and ii) sends a signal either toclose said second valve arrangement or to allow said second valvearrangement to remain open so that a flow of the chemical composition isprevented from said at least one chemical containing unit to said dosingunit.
 9. The system of claim 8, wherein said dosing unit comprises: adosing unit reservoir configured to receive a flow of the chemicalcomposition from said at least one chemical containing unit and direct aflow of the chemical composition from said dosing unit to said chemicaldelivery unit; and a dosage element configured to receive a flow of thechemical composition from said dosing unit reservoir and direct a flowof the chemical composition to said dosing unit reservoir, said dosageelement also configured to add the selected dose to the chemicalcomposition, wherein in response to said algorithm determining that thesystem should operate in the dosing mode, said controller i) sends asignal to and actuates said first valve arrangement to prevent a flow ofthe chemical composition from said at least one chemical containing unitto said dosing unit, and sends a signal to and actuates said secondvalve arrangement to allow a flow of the chemical composition from saidat least one chemical containing unit to said chemical delivery unit.10. The system of claim 9, wherein: said first valve arrangementcomprises a first valve, a first conduit in fluid communication with andextending from said chemical containing unit to said first valve, and asecond conduit in fluid communication with and extending from said firstvalve to said dosing unit, said first valve disposed intermediate saidfirst and second conduits, wherein an open position of said first valveallows a flow of the chemical composition from said first conduit tosaid second conduit and a closed position of said first valve prevents aflow of the chemical composition from said first conduit to said secondconduit; said second valve arrangement comprises a second valve, a thirdconduit in fluid communication with and extending from said firstconduit to said second valve, and a fourth conduit in fluidcommunication with and extending from said second valve to said chemicaldelivery unit, said second valve disposed intermediate said third andfourth conduits, wherein an open position of said second valve allows aflow of the chemical composition from said first conduit to said fourthconduit via said third conduit and a closed position of said secondvalve prevents a flow of the chemical composition from said thirdconduit to said fourth conduit.
 11. The system of claim 10, wherein saidat least one chemical containing unit is an electroplating bath of awafer electroplating tool.
 12. The system of claim 5, wherein whereinsaid at least one chemical containing unit is an electroplating bath ofa wafer electroplating tool.
 13. The system of claim 1, wherein said atleast one chemical containing unit comprises at least two chemicalcontaining units.
 14. The system of claim 13, further comprising: aplurality of chemical containing unit outlets, said plurality equal tothe number of said at least two chemical containing units, wherein eachof said chemical containing unit outlets is associated with a respectiveone of said at least two chemical containing units; a chemicalcontaining unit outlet manifold in fluid communication with saidplurality of chemical containing unit outlets; a chemical containingelement outlet reservoir in fluid communication with said chemicalcontaining unit outlet manifold and said dosing unit.
 15. The system ofclaim 14, wherein wherein said at least one chemical containing unit isan electroplating bath of a wafer electroplating tool.
 16. A method formonitoring, dosing and distribution of a chemical composition in achemical treatment process, the chemical composition containing at leastone additive for maintaining quality of the chemical treatment process,comprising the steps of: a) allowing the chemical composition to flowfrom at least one chemical containing unit to a dosing unit; b)monitoring a property of the chemical composition with an online monitorat a location intermediate the chemical containing unit and the dosingunit or at the dosing unit; c) sending from the online monitor to acontroller a signal associated with the monitored property; d)determining at the controller whether the at least one additive shouldbe added to the chemical composition at the reservoir based upon themonitored property, thereby resulting in a decision to add or not aselected amount of the at least one additive to the chemical compositionat the reservoir based upon the signal from the online monitor; e)sending from the controller to the dosing unit a signal associated withthe decision; f) allowing the selected amount of the at least oneadditive to be added or not be added to the chemical composition at thedosing unit in response to the signal associated with the decision; g)allowing the chemical composition to flow from the dosing unit to thechemical containing unit.
 17. The method of claim 1, further comprisingthe steps of: determining by the controller a rate of depletion over adepletion time period of at least one of the at least one additive inthe chemical composition based upon a concentration of the at least oneof the at least one additive measured by said monitor in comparison to aconcentration of the at least one of the at least one additivepreviously measured by said monitor; predicting by the controller anamount of at least one of the at least one additive that when added tothe chemical composition will maintain a concentration of the additivewithin a predetermined concentration range around a predeterminedsetpoint concentration; and correcting by the controller the predictedamount by adding to, or subtracting from, the predicted amount, anamount of the at least one additive based upon a previous concentrationof the at least one additive measured by said monitor, wherein thecorrected amount is the selected dose.
 18. The system of claim 17,wherein the at least one chemical containing unit is an electroplatingbath of a wafer electroplating tool.
 19. The system of claim 16, whereinthe at least one chemical containing unit is an electroplating bath of awafer electroplating tool.
 20. The system of claim 16, wherein said stepof allowing the chemical composition to flow from the dosing unit to theat least one chemical containing unit comprises: allowing the chemicalcomposition to flow from the dosing unit to a chemical delivery unit;and delivering the chemical composition from the at least one chemicaldelivery unit to the chemical containing unit.
 21. The system of claim20, further comprising the steps of: providing a first valve arrangementin fluid communication with the chemical containing unit and the dosingunit, the first valve arrangement configured to allow or prevent a flowof the chemical composition from the chemical containing unit to thedosing unit; and providing a second valve arrangement in fluidcommunication with the chemical containing unit and the chemicaldelivery unit, the second valve arrangement configured to allow orprevent a flow of the chemical composition from the chemical containingunit to the chemical delivery unit.
 22. The system of claim 21, furthercomprising the step of: determining by the controller whether to performsaid method in a main recirculation mode in which the first valvearrangement allows a flow of the chemical composition from the at leastone chemical containing unit to the dosing unit and the second valvearrangement prevents a flow of the chemical composition from the atleast one chemical containing unit to the dosing unit, or in a dosingmode in which the first valve arrangement prevents a flow of thechemical composition from the chemical containing unit to the dosingunit and allows a flow of the chemical composition from the at least onechemical containing unit to the chemical delivery unit, therebyresulting in a mode decision.
 23. The system of claim 22, furthercomprising the step of: in response to the processor determining thatsaid method should be performed in the main recirculation mode, sendinga signal to either open said first valve arrangement or to allow saidfirst valve arrangement to remain open so that a flow of the chemicalcomposition is allowed from said at least one chemical containing unitto said dosing unit.
 24. The system of claim 22, further comprising thestep of: in response to the processor determining that said methodshould be performed in the dosing mode, i) sending a signal either toclose the first valve arrangement or to allow the first valvearrangement to remain closed so that a flow of the chemical compositionis prevented from the at least one chemical containing unit to thedosing unit, and ii) sending a signal either to open the second valvearrangement or to allow the second valve arrangement to remain open sothat a flow of the chemical composition is allowed from the at least onechemical containing unit to the chemical delivery unit.
 25. The methodof claim 24, further comprising the steps of: providing the dosing unitwith a reservoir and a dosage element; sending by the controller asignal to the dosage element to add the selected amount to a flow of thechemical composition from the dosing unit reservoir; adding by thedosage element the selected amount to the flow of chemical compositionfrom the dosing unit reservoir; and allowing the combined flow of theselected amount of the at least one additive and the chemicalcomposition to flow from the dosage element to the dosing unitreservoir.
 26. The method of claim 17, wherein said at least onechemical containing unit is an electroplating bath of a waferelectroplating tool.
 27. The method of claim 23, wherein said at leastone chemical containing unit is an electroplating bath of a waferelectroplating tool.
 28. The method of claim 24, wherein said at leastone chemical containing unit is an electroplating bath of a waferelectroplating tool.
 29. The method of claim 16, wherein said at leastone chemical containing unit comprises at least two chemical containingunits.
 30. The method of claim 29, comprising the further steps of:providing a plurality of chemical containing unit outlets, the pluralitybeing equal to the number of the at least two chemical containing units,wherein each of the chemical containing unit outlets is associated witha respective one of the at least two chemical containing units;providing a chemical containing unit outlet manifold in fluidcommunication with the plurality of chemical containing unit outlets;providing a chemical containing unit outlet reservoir in fluidcommunication with the chemical containing unit outlet manifold and thedosing unit; allowing a flow of the chemical composition from theplurality of chemical containing unit outlets to the chemical containingunit outlet reservoir; and allowing a flow of the chemical compositionfrom the chemical containing unit outlet reservoir to the dosing unit.31. The method of claim 30, wherein said at least one chemicalcontaining unit is an electroplating bath of a wafer electroplatingtool.
 32. The system of claim 2, wherein the processor is programmedwith the algorithm such that the amount added to or subtracted from thepredicted amount is based upon at least two previous measurements bysaid monitor of the concentration of the at least one additive.
 33. Thesystem of claim 2, wherein the processor is programmed with thealgorithm such that a time in between additions of the at least oneadditive is less than the time in between measurements by said monitor.34. The system of claim 34, wherein the processor is programmed with thealgorithm such that a frequency of additions of the at least oneadditive by said dosing unit may be varied.
 35. The system of claim 2,wherein the processor is programmed with the algorithm such that thepredicted amount is also based upon a derivative of the depletion rate.36. The system of claim 2, wherein the processor is programmed with thealgorithm such that the predicted amount does not depend upon a variablecondition at said chemical containing unit.
 37. The system of claim 2,wherein the processor is programmed with the algorithm such that thepredicted amount does not depend upon a time interval between successivemeasurements by said monitor.
 38. The method of claim 17, wherein theamount added to or substracted from the predicted amount is based uponat least two previous measurements by the monitor of the concentrationof the at least one additive.
 39. The method of claim 17, furthercomprising the step of: varying a time interval between additions of theat least one additive such that the time in between additions is lessthan a time interval between measurements by said monitor.
 40. Themethod of claim 39, further comprising the step of: varying a frequencyof additions of the at least one additive by said dosing unit.
 41. Themethod of claim 17, wherein the predicted amount is also based upon aderivative of the depletion rate.
 42. The method of claim 17, whereinthe predicted amount does not depend upon a variable condition at saidchemical containing unit.